This article discusses the impact of declining British power and increasing Commonwealth immigration on religion in England after the Second World War. It argues that a diminishing sense of Britain's greatness undermined the belief that England was a Christian nation, a belief common among Britain's elites, especially members of the Conservative party, and one that had long undergirded Christian faith and practice in the country. The language of Christian nationhood became toxic as it became associated with unpopular white settler governments in southern Africa. Moreover, the debates over the 1962 Commonwealth Immigrants Act show how the migration of non-Christian religious groups to England had created a situation in which those who wished to continue to speak of the country as Christian would be accused of racism, a charge with fresh bite at that time. The article argues that international contexts deserve greater attention in the study of religious change.